This three-volume set contains selected papers arising from a conference held in 1991 on precipitation and air pollution. The first volume addresses the precipitation scavenging process; the second deals with atmosphere-surface exchange processes; and the third covers air pollution and deposition.

The ITM conference series has always had a strong spirit of cooperation under the NATO/CCMS umbrella, and with the considerable interest fram Partner countries to participate in the ITM conferences, it provides an excellent opportunity to create ties between scientists. Whereas all previous ITM conferences have taken place in NATO countries, the 23rd ITM takes place in a Cooperative Partner country, Bulgaria, and is hosted by the National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences. This fact reflects a general wish for a closer connection and collaboration among scientists fram Partner and NATO countries. This volume contains the papers from the 23rd NATO/CCMS International Technical Meetings on Air Pollution Modelling and Its Application, being held September 28 - October 2, 1998, at Riviera Holiday Club, Varna, Bulgaria. It was attended by 120 participants from 30 countries. Thanks are due to all who made it possible to plan, carry through, and follow up the meeting, and to the participants who made the conference so successful. Special thanks are due to the sponsoring institutions: ATO/CCMS EURASAP RIS0 BAS 3M NATO/CCMS - Committee on the Challenges of Modem Society EURASAP - European Association for the Science of Air Pollution RIS0 - Ris0 National Laboratory, Denmark NIMH - National Institute of Meteorology and Hydralogy, Bulgaria BAS - Bulgarian Academy of Sciences 3M Representation office, Bulgaria Prestige Business Ltd. , Bulgaria The excellent collaboration with CIM (Company for International Meetings Ltd.

Among the chemical and physical processes involved in the transformation of pollutants between their sources and their ultimate deposition, those associated with clouds, aerosols and precipitation must be rated as the most difficult both to study and to understand. This book presents a variety of recent advances in this field, including the properties and composition of aerosol particles, chemical transformation and scavenging processes, the relationship between liquid-phase chemistry and cloud micro-physics, entrainment, evaporation and deposition, trends in high Alpine pollution, transport processes, and developments in instrumentation. This book is Volume 5 in the ten-volume series on Transport and Chemical Transformation of Pollutants in the Troposphere.

A major environmental concern is the increasing burden on all scales of photo-oxidants, acidifying substances and potential nutrients in the troposphere. These lead to episodes of summer smog, and appreciable damage to eco-systems both on land and at sea. Underlying the environmental effects is the complex scientific problem of linking the man-made and biological emissions to the myriad chemical reactions that transform the pollutants as they are transported to and deposited in the surroundings and also pristine areas remote from the sources. The project, the scientific results of which are described in this book, was set up to study the problem in an inter-disciplinary way by co-ordinating the work of more than 150 research groups in some 20 countries.

Polar ice cores have provided tremendous advances in our knowledge of past climate change. They also contain an archive of geochemical data, which can certainly delineate some of the forcing factors that govern climate change. However, our ability to interpret these data is severely curtailed by lack of knowledge of the processes governing the transfer of chemical species from the air to the snow. This book outlines the potential and problems of ice core chemistry and discusses the processes involved in air-snow transfer. It gives the state of current knowledge and an agenda for future research.